Characteristics of Keratoconic Patients Attending a Specialist Contact Lens Clinic in Kenya.

PURPOSE: To describe the characteristics of keratoconus (KC) patients seen in a contact lens clinic of a children's hospital in Kenya.
RESULTS: A total of 254 patients' records were analyzed. Mean age at presentation to the clinic was 20.97 ± 11.13 year (range, 6-84 years) with 75% between the ages of 6 and 25 years. There was a preponderance of males (59.8%). Most patients were referred by an ophthalmologist. All patients were Africans. The most common complaints were blurred vision (50%), poor visual acuity with spectacles (33.5%), contact lens intolerance (11.8%), and other (unspecified). Most cases were severe (71%) followed by moderate (22.9%) and mild (6.2%). Mean BCVA was 0.24 ± 0.23 (6/11). An optical correction was provided in 98% of cases; 34.6% with spectacles, 31.1% with gas permeable lenses and the remaining with both. Referral for keratoplasty was warranted in 16.5%.
CONCLUSION: This is the first study of KC conducted in Kenya. KC presented at a very early age and tended to be severe. Ophthalmologists were the main source of referral. The main presenting symptom was reduced vision. Optical correction was the most common management and the percentage of patients referred for surgery concurred with other studies.

Introduction

The characteristics of keratoconus (KC) have been well documented in numerous populations worldwide. Characteristics such as age, gender, visual acuity, severity, associated factors, and management have been reported in studies conducted in Australia,[1] England,[2] India,[345] Iran,[6] Israel,[7] Jordan,[8] Malaysia,[9] New Zealand,[10] Scotland,[11] Singapore,[12] Turkey,[13] and United States.[14151617]

To the best of our knowledge, there is no published study, from Africa, of the characteristics of KC. The aim of the present study is to provide the first description of patients diagnosed with KC in an African community seen in a specialized contact lens clinic at a children's hospital in Kenya.

Methods

A retrospective chart review was performed on all the ophthalmic records of patients with KC evaluated at the Muthaiga Eye Clinic at Gertrude's Children Hospital in Nairobi, Kenya from January 2007 to October 2014. All patients included in this had been initially diagnosed with KC by an ophthalmologist and referred either directly or through a third party to this clinic. Data were collected on gender, age at initial presentation, source of referral, main complaint at referral, severity of KC, best-corrected visual acuity (BCVA), prior management, if any at first presentation, including optical correction, collagen cross-linking, and keratoplasty. During the study, more data were collected including management and the outcome of treatment. This study was approved by the African Medical Research Foundation, Kenya and Cardiff University, UK. Patients with systemic or ocular pathology (other than KC) were excluded, as well as those whose records were incomplete.

Corneal curvature was measured with a keratometer (Bausch and Lomb, Rochester, NY, USA). The severity was assessed based on the classification used in the Collaborative Longitudinal Evaluation of KC study,[16] which is: Mild KC <45 D in both meridians, moderate KC 45–52 D in one or both meridians, severe KC >52 D in one or both meridians. Visual acuity was determined using a Keeler (finesse) Snellen chart at 3 m. Snellen readings were converted to logMAR.

Data were analyzed using SPSS version 20.0 (IBM Corp., New York, NY, USA). Normality of data was assessed with the Kolmogorov–Smirnov test. If normality was satisfied, the t-test and Chi-square test was used. In cases of nonnormal distribution, the Mann–Whitney test for two independent variables was used or the Kruskal–Wallis test was if there were more than two groups. All tests were two-tailed, and P < 0.05 was considered statistically significant.

Results

The ophthalmic records of 254 patients were reviewed. The mean age at presentation was 20.97 ± 11.13 years (n = 249 patients; age was not recorded in the charts of five patients). The age data were not normally distributed (Z = 0.157, P < 0.001) and slightly skewed towards the younger age (median 18.0). The ages ranged between 6 and 84 years although 75% of the patients were between the age of 6 years and 25 years. The percentage of male subjects was higher (59.8%, n = 152) than female subjects (40.2%, n = 102), (P = 0.002), resulting in a ratio of 3:2. The mean age at initial presentation was 21.06 ± 11.91 years (range, 6–84 years) for males and 20.84 ± 9.93 years (range, 7–71 years) for females. All patients were African (99%) mainly from a low socioeconomic background.

Ophthalmologists referred 67.3% of the patients. The remaining patients were directed by a teacher (6.7%) or other sources, or very rarely an optometrist (0.4%), they had all been diagnosed initially by an ophthalmologist. About one-third of patients at first presentation had no refractive correction (33.9%). The remaining patients were managed with spectacles (28.7%), contact lenses (19.7%), or a combination of spectacles and contact lenses (17.7%). Of these patients, 5.1% had undergone collagen cross-linking, and 9.1% had undergone keratoplasty.

The most common patient complaints at initial presentation was blurred vision (50%) followed by poor visual acuity with spectacles (33.5%), contact lens intolerance (11.8%), unspecified (4.3%), and frequent change in refraction (0.4%).

Corneal curvature data were available in only 306 eyes as data were missing in the remaining eyes or the keratometric data were removed for eyes that had undergone corneal transplantation. Based on the keratometry data available, 98.3% of the patients had bilateral KC of whom 6.2% had mild KC, 22.9% had moderate KC and 71% KC had severe KC. Mean binocular BCVA (n = 248) was 0.24 ± 0.23 (n = 248) and the median was 0.20, indicating a distribution skewed toward better visual acuity. Seventy-five percent of KC patients had binocular BCVA of 0.4 logMAR (6/15) or better. BCVA was 0.37 ± 0.38 for right eyes (n = 234) and 0.36 ± 0.36 (n = 233) for left eyes.

The age at initial presentation and the corresponding BCVA of the eyes of different severity are given in Table 1. The BCVA data were not normally distributed (Z = 0.197, P < 0.005). Patients with severe KC presented at an earlier age and had poorer visual acuity than those with mild and moderate KC (P < 0.005).

Table 1

Age at first presentation and best corrected visual acuity of eyes with keratoconus based on severity

Although 66.1% of the patients had refractive correction at presentation after assessment, 98% required some form of refractive correction, 2% required no refractive correction. Of those corrected, 34.6% were prescribed spectacles, 31.1% received gas permeable contact lenses and 32.3% were prescribed both spectacles and contact lenses and 16.5% of the patients were referred for keratoplasty. The reasons for referral were poor BCVA with optical correction (55.2%), inadequate contact lens fitting (20.7%), hydrops (13.8%), and contact lens intolerance (10.3%). After keratoplasty, 92% required spectacles, 4% required contact lenses, and 4% required contact lenses and spectacles.

Discussion

In Kenya, KC is occurring in people as young as 6 years of age. Such early occurrence has also been reported in Iran.[6] At an initial presentation, a large proportion of patients in the present study were very young (75% were between the ages of 6 years and 25 years). Notably, however, the age at presentation does not usually represent the age of disease onset, which is usually younger as the development of the disease is generally insidious and asymptomatic, and the patients had already been diagnosed by an ophthalmologist before referral. Table 2 presents the age of initial presentation or diagnosis reported in various studies. Previous studies from India, Iran, Malaysia, Israel, and Jordan are similar to those obtained in the present study [Table 2]. However, KC seems to occur at a somewhat older age in the US and among Caucasians in the UK. Younger age at presentation means that the condition has an earlier onset and most likely faster progression in African, Middle Eastern and Indian populations.[32324] The higher proportion of bilateral cases in this study (98.3%) substantiates faster progression of the disease developing in the less affected or sub-clinical fellow eye. Early occurrence of the disease suggests a more severe form of the disease, which progresses more rapidly to surgery.[61425] Contrary to this observation, a lack of correlation between severity and age of onset was reported in one study.[9] Early onset may reflect the variability of the disease process and genetic differences between the various ethnic groups for which some evidence has been reported.[926] The high proportion of bilateral cases in the current study concurs with other studies, where only 0.5% of patients had unilateral KC which was documented using the same procedure.[2728] In contrast, 14.2% of bilateral cases were reported in a study of 600 eyes conducted before the development of corneal topography.[29]

Table 2

Mean age of keratoconus patients at initial presentation, diagnosis, or self-reported onset of the disease in various countries

The preponderance of males with KC in the current study is consistent with the majority of studies published in the last 30 years.[210303132] Papers published over 30 years ago report the opposite gender distribution.[29] In a retrospective study from the Netherlands[33] using data from over 100,000 contact lens wearers from four university clinics and five contact lens centers between 1950 and 1986, the ratio of males-to-females remained < 1.0 until the 1970s when the ratio significantly increased and reached 1.58 for patients diagnosed in 1985 and 1986. The cause of this difference remains unclear. A male majority may be explained by hormonal differences, and it has been noted that KC develops more rapidly in males than females[34] which could account for the higher prevalence in some study samples. There could also be a gender bias in some societies where services are offered more so to males than females.

The source of referral in Kenya differs markedly from that in Western countries. In Kenya, the majority of referrals came from ophthalmologists similar to Iran.[6] In the UK and Scotland, optometrists were the main source of referrals (72.2% and 79%, respectively).[211] In a large study conducted at Moorfields Eye Hospital in London, it was noted that “KC was diagnosed in the vast majority of patients by optometrists.”[14] However, in Kenya patients are generally more likely to follow the advice of physicians such as ophthalmologists rather than nonphysician care providers.

The most common complaint of the subjects was blurred vision followed by poor visual acuity with spectacles (83.5% total) which is consistent with the large number of cases of severe keratoconus (71%) who exhibited significantly poorer acuity than either patients with moderate or mild KC. This observation concurs with two other retrospective studies in the UK that reported symptoms of blurred vision of 78%[2] and 93%.[11] Other complaints were contact lens intolerance (11.8%) followed by unspecified reasons and frequent change in refraction.

A high percentage of the patients in the current study had severe KC, which is not surprising as the study sample was from a hospital eye clinic to which patients are referred to by primary or secondary eye care practitioners and the age of presentation was younger. Similar results are reported from studies from India and Jordan [Table 3] from hospital contact lens clinics, except studies from the USA.[16] In this study, 66.1% of the patients used some form of correction at presentation, 37.4% of whom had already been prescribed rigid contact lenses by a secondary eye care practitioner and 14.2% of the patients had already been treated by other specialists with either collagen cross-linking or keratoplasty before referral to this tertiary contact lens clinic.

Table 3

Severity of keratoconus reported in several studies from different countries

Management of the vast majority of patients (98%) was with some form of optical correction, which provided very good visual acuity and 72% of eyes had a BCVA ≥0.3 logMAR (6/12). Only rigid gas permeable contact lenses were used because the cost of hybrid lenses is too high for the patients presenting to this clinic and soft lenses were inappropriate for such irregular corneas. In the current study, 16.5% of patients were referred for corneal transplantation because optical correction was inadequate. This proportion of referral to corneal transplantation is well within the range of 2%–29% reported in other studies (with one outlier) [Table 4]. However, recent studies report lower percentages of referral to keratoplasty likely due to the well-documented success of corneal collagen cross-linking.[913] For example, a study from Malaysia reported 52% of patients were prescribed contact lenses, 24% had cross-linking, and only 2.5% had a corneal graft procedure.[9]

Table 4

Percentage of keratoconus patients who have undergone unilateral or bilateral keratoplasty

There are some limitations to this study. Although this was a retrospective study conducted over a few years, all assessments were performed by the same practitioner. However, some data were missing from the records which may affect outcomes. In addition, this is a hospital-based study, and the patients may have a more severe form of the KC compared to cases presenting to a routine eye care practice. The percentage of patients prescribed contact lenses would most likely be higher if hybrid or other customized lenses could have been used; however, these lenses were cost-prohibitive for most patients in this study.

Conclusion

This is the first study describing a cohort of KC patients from a tertiary hospital clinic in Kenya, and to the best of our knowledge, in Africa. The vast majority of patients were referred to this clinic by ophthalmologists which is similar to Middle Eastern countries. The age at referral tended was low with some cases as young as 6 years of age, which concurs with the findings in the Middle East and India where there is a high prevalence of KC compared to Europe and the US. A study of the prevalence of KC in Kenya is needed. The percentage of patients requiring corneal graft and the reasons for this procedure was similar to other studies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.[36]